Ion implantation is a standard technique for introducing property-altering impurities into substrates. A desired impurity material is ionized in an ion source, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the substrate. The energetic ions in the beam penetrate into the sub-surface of the substrate material and are embedded into the crystalline lattice of the substrate material to form a region of desired conductivity or material property.
In conventional beamline ion implantation processes, ions are provided toward a substrate in beams that may comprise generally parallel ions. Thus, for a given substrate orientation with respect to the ion beam principle axis, the ions impinge at the same angle of incidence. This facilitates control of implantation of ions into the substrate since for any given substrate orientation, the direction of ion implantation is well characterized. However, when multiple angle implantation is desired, it is necessary to move the substrate orientation or beam direction. Moreover, the ion beam generally covers a wide area of the substrate, requiring masking in order to implant only desired areas.
Recently, techniques and apparatus have been developed to provide ions to a substrate over a range of angles. FIG. 1 is a block diagram that depicts a plasma processing apparatus that provides ions at multiple angles to a substrate. The system 400 includes a plasma source 401, an extraction plate 11 (or sheath engineering plate), and a process chamber 402. A gas source 404 is connected to the plasma source 401. The plasma source 401 or other components of the system 400 also may be connected to a pump (not shown), such as a turbopump. As illustrated, the plasma source 401 is an RF plasma source with an RF source generator 408 and an RF matching network 409. The plasma source 401 is surrounded by an enclosure 411 and a DC break 410 separates the enclosure 411 from the process chamber 402. The process chamber 402, plasma source 401, or platen 403 may be grounded.
The extraction plate 11 is used to extract ions 102 for implantation into a workpiece (substrate) 100. The extraction plate 11 may be cooled. The plasma source 401 may be biased and a bias power supply (not shown) may be provided to provide a continuous or pulsed bias on the substrate with respect to the plasma 140 to attract the ions 406. The extraction plate 11 may have at least one aperture 407, through which ions 102 are provided to substrate (workpiece) 100. Additional description related processing systems can be found in U.S. patent application Ser. No. 12/417,929, filed Apr. 3, 2009, and issued as U.S. Pat. No. 7,767,977; Ser. No. 12/418,120, filed Apr. 3, 2010; Ser. No. 12/644,103, filed Dec. 22, 2009; and Ser. No. 12/848,354, filed Aug. 2, 2010, each of which is herein incorporated in its entirety by reference.
An ion beam extracted from a plasma using system 400 may be used to simultaneously provide to substrate 100 ions over a range of angles if desired without requiring complicated masking or lithography procedures. In view of the above, it will be appreciated that it may be useful to provide improvements to such a system that facilitate additional capabilities for processing substrates.